Electric regulating system utilizing a phase reversing reactive compensator



May 12, 1953 D. J. SIKORRA ELECTRIC REGULATING SYSTEM UTILIZING A PHASEREVERSING REACTIVE COMPENSATOR Filed Dec. 2, 1950 VOL 71465 PEGl/LA 727APatented May 12, 1953 ELECTRIC REGULATIN G SYSTEM UTILIZING A PHASEREVERSING REACTIVE COM- PENSATOR Daniel J. Sikorra, Milwaukee, Wis.,assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application December 2, 1950, Serial No. 198,814

5 Claims.

This invention relates in general to regulating systems fordynamoelectric machines, and in particular to reactive currentcompensators for such regulating systems.

When synchronous dynamoelectric machines which are equipped with voltageregulators are connected in parallel directly to a bus bar or through atie line of negligible impedance, it is customary to reactivelyunder-compound at least one of the machines to avoid an uncontrolledexchange of reactive current between the machines. If a machine isconnected to a line through transformers, the reactance of thetransformers and the tie line may cause an excessive voltage droptherein, necessitating the reactive overcompounding of the machine tomaintain the voltage delivered by the transformer at its desired value.Such over-compounding or undercompounding is usually accomplished byenergizing an impedance device by a measure of the current delivered bythe machine, usually through one or more current transformers, andimpressing the voltage of the impedance device on the voltage regulatorin a direction to produce the desired compounding.

However, such systems produce only one type of compounding for a givenconnection, and require a reversal of the current transformerconnections or the impedance device connections to produce the oppositetype of compounding. Since it may be desired to operate a given machineunder-co-mpounded for a length of time and then, because of a change inoperating conditions, operate the machine over-compounded, the abovesystems have the disadvantages of necessitating the reversal of theconnections of the impedance device or the short circuiting of thecurrent transformer to reverse the connections thereof, if it is desiredto change the type of compounding provided.

These disadvantages can be overcome by providing a compensator whichprovides for overcompounding or under-compounding a regulated machinewithout reversal of any connections or short circuiting of any elements.

It is therefore an object of the present invention to provide animproved reactive drop compensator for regulated dynamoelectricmachines.

It is a further object of the present invention to provide a reactivedro compensator which will produce over-compounding or under-compoundingof a regulated machine without reversal of any connections or shortcircuiting of any elements of the compensator.

Objects and advantages other than those outlined above will be readilyapparent from the following detailed description when read in connectionwith the accompanying drawing, in which:

Fig. 1 diagrammatically illlustrates a regulating system embodying theapparatus and circuits of the invention;

Fig. 2 is a diagram vectorially illustrating the relationship betweenthe electric quantities of the regulating system shown in Fig. 1; and

Fig. 3 partly illustrates an alternate embodiment of the apparatus andconnection of Fig. 1.

Referring to Fig. 1, the invention is shown applied to the regulation ofa dynamoelectric machine 5 supplying an alternating current load circuitrepresented by conductors 6, I, 8. Machine 5 is provided with anarmature 5a and a field winding 52) supplied with excitation currentfrom the armature Illa of a generator 10. Generator Ill is provided witha self-exciting field winding lilb connected to armature Illa in serieswith an adjustable resistor 4 and the armature Ho, of a buckboostexciter ll. Resistor 4 is preferably so adjusted that field winding lflbprovides all the excitation required to maintain the voltage of armature10a at any given value. Exciter l l is provided with a control fieldwinding Ilc, which is deenergized when the voltage of machine 5 has thedesired value and which is directionally energized through conductorsI2, l3 from a voltage responsive circuit in response to variations inthe voltage of machine 5 above and below the desired value.

Connected. across conductors 6, l, 8 to be energized by the voltage ofmachine 5 are the primary windings I3 of transformers I4. Secondarywindings I 5 of transformers M are connected to autotransformers I6 andbooster transformers I! to provide a smooth adjustment of the voltagesupplied to the voltage responsive circuit. The voltage responsivecircuit or regulator,

shown in the drawing as block l8, may be of any suitable known type, butis preferably of the nonlinear resonant type disclosed and claimed in mycopending application Serial No. 114,751, filed September 9, 1949. Theregulator I8 is energized through terminals 2| with three voltages whichare measures of the voltages of conductors 6, T, 8, and the regulatorwill operate to produce at its output terminals 22 a unidirectionalvoltage responsive to deviations in the average value of the voltagesimpressed on terminals 2| from a predetermined value. If no reactivecompensator were utilized with regulator 18, it will be understood thatthe common terminal of transformers It; would be connected directly tothe middle terminal 2| of regulator. 18. The output control voltage atterminals 22 will have a polarity and magnitude dependent upon the"direction and magnitude of variation in the average value of thevoltages impressed on terminals 2| from the predetermined desired Value}andithis output voltage is supplied "to field-winding 'Ilc throughconductors I2, [3 to produce across armature lla a voltage ofaepolar-ity'andr magnitude to cause the voltage ofmachine 5 to-return tosubstantially the predetermined value.

As stated above, it may be desired to either over-compound orunder-compound machine fi, and for this purpose, regulator i8 issupplied with acompensating control voltage of variable phase andmagnitude A current transformer 23' is connected to conductor 7 toproduce across its terminals a voltage proportional to the current inconductor 1'. Connected across current transformer 23 are anautotransformer 24 provided with an adjustable tap Z5 and a suitablereactive impedance device; such as an inductive reactor 25, providedwith an intermediate tap 21. The primary winding 28 of an isolatingtransformer 29 is connected between adjustable tap 25 and intermediatetap 2'5, and the secondary winding 3Lof transformer 29 is connected;between a terminal}! of regulator lfi and the common terminal ofsecondary windings l5. The impedance of autotransformer 24 isconsiderably higher than theimpedance of reactor 25,so'that nearly all'of the current supplied-by current transformer, 2,3 flows through.reactor 26 and the power factor, of the Ci10l1it 'isfdetermined almostentirelyb-y reactor v26. ''i iutotransforn'i'er 24' and reactor 26 forma bridge circuit with input'terminals defined by the 'terminals'ofcurrent transformer. '23 and output terminals represented byintermediate movable. tap 25 and intermediate tapZL H The operation ofthe compensator may readily be understoodfbyreference to Fig. 2,in-which the vectors AB, BC, CA represent the voltages betweenconductors 6, 1-, Sand the vectors, a, h, represent the currents inconductors-6, 1, 8, if the load circuit operates at unity. power factor.The voltage across reactor 26 and autotransfcrmer 2 3- will lead thecurrent in current transformer 23 .by nearly 9o degreesand will have theposition. represented by vector BD- when the current bis at unitypowerfactor. Assuming that machine is connected-directly to a bus barinparallel with other-regulated machines, it is necessary tounder-compound machine 5. Under these circumstances. adjustable tap ismoved away from thecenter of autotransformer 24 an amount determined bythe amount ofcompensation desired. This will produce a voltagedifference between the terminal 21 and the adjustable tap 25, to'impresson primary winding 28 a,-voltage in phase with voltage BD.Secondary wind-ingtil will have induced therein a voltage proportionalto the voltage of Winding 28 and willzimpress'this voltage on regulator18. This voltage will have amagnitude. dependent upon the setting of tapZ5 and for a representative compensator, will have a magnituderepresented by vector BD'. Regulator :8 will therefore have impressedthereon at its input terminals 2!, the voltages AD, DC, CA and willoperate to maintain the average value of voltages AD, DC, CA constant.However, the average value of these voltages does not differ appreciablyfrom the average value of voltages AB, BC, CA and, the compensator ofthis invention therefore has a negligible effect upon the operation ofregulator l8 atgunitypower factor.

Howevenif the power factor of the load circuit becomes lagging for anyreason, the voltage of autotransformer 24 and reactor 26 will beretardedfipphase, until at degrees lagging powei' factor -the voltageacross the compensator elements will'be represented by vector BE. This.Willprodii'de in secondary winding 30 a voltage represented byvector BEand will cause regulator I B-to maintain the average value ofvoltages-A113 E'C, CAsubstantially constant. From Fig. .2, his apparentthat the average value of voltages AE', E'C, CA is considerably higherthan the average value of voltages AB, BC, CA, and therefore} regula'timt8 reduces the voltage of machine 5 through field winding lie to a valueless 'thanthe machine voltage at unity power factor. For values of powerfactorbetween one and Zer','- the voltages'supplied 'by the compensator'will have vector positions intermediate vectors BD' and BE' to causethe terminal voltage' of'th' machine to decrease with decreasing powerfactor fOr prOduc'ing the desired undercompounding. i V

- Iii-machine '5 shouldsubsequently be-"co'nne'cted to a' transformerhaving an appreciable impedance and which it' is desired to'maintain acdn'stai'it butput voltage regardless-oi variations inthe power factorof conductors 6,158, it'is necessary to over-compound machine '5. 'Thisis accomplished by moving tap 25 td the opposite side 'of the midpointofautotfaiisformer 24 an amoiintdependent upon the amount ofcompensatiofidesired: This reverses: the pliase 'o'f the voltages orwmsm s 28;. 30 so that the voltage impressed on regulatorl'fl'by"winding 3G is representedjby vector BF at unity powerfacton' I"heaverageval'iieof voltag'es 'AF, F'C, CA "do'es not difier appreciablyfrom th'e' averag e value of voltages Al':f-il3(l% CA so that the effectof the compens tor-remain negligible at unity factor.

At iero p'dwer factor the voltage of winding 31yis represehtd'by vectorBF, and it is ap parent that the average value of voltages AP, F'C;- 3Ais considerably less than the average value of voltagesAB, BC, CA,causing regulator It 'to 'increase the voltage of machine 5. For valuesofpower factor between unity and zero, the voltages ofsecondary winding30 have vector positions intermediate vectors BF; BF, so that thevoltage of machine 5 is increased in response to variations in the powerfactor in the load circuit to produce the desired" overcompounding. Itis apparent that the voltage of secondary winding SB-varies in magnitudein response to variations in" the magnitude of the current in.

duce the desired compensation. The operation of the compensator withcapacitors 32 in place of reactor 26 is identical to that describedabove except that the phase of the compensating voltage supplied bywinding 30 is reversed with respect to its phase when reactor 26 isused, for any given position of tap 25 except the center position.'Ehcrefore, to under-compound machine when using capacitors d2, tap 25of a-utotransformer 25 is moved to the opposite side of midpoint ofautotransformer 24 from its position when under-compounding with reactor26, and vice versa.

Although but two embodiments have been illustrated and described, itwill be apparent to those skilled in the art that various changes andmodifications may be made therein without departing from the spirit oi?the invention or from the scope of the appended claims. In particular,although the compensator of this invention is illustrated in connectionwith a polyphase load circuit, it will be readily apparent that thecompensator will function effectively when utilized in connection withsingle phase systems.

It is claimed and desired to secure by Letters Patent:

1. In combination, an alternating current generator, a load circuitconnected to said generator, regulating means for controlling thevoltage of said generator, a current transformer connected in said loadcircuit, an autotransformer having an intermediate tap, a capacitiveimpedance device having an intermediate terminal, means connecting saidimpedance device and said autotransiormer in parallel with each otheracross said current transformer, means connected between said tap andsaid terminal for producing a control voltage which varies in magnitudeand phase in dependence upon the magnitude and phase of said loadcurrent, means for varying the adjustment of said tap to reverse thephase of control voltage, and means for impressing said control voltageon said regulating means to cause said regulating means to vary thevoltage of said generator in response to variations in the phase andmagnitude of said load current.

2. in combination, an alternating current generator, a load circuitconnected to said generator, regulating means for controlling thevoltage of said generator, a current transformer connected in said loadcircuit, an autotransformer having an intermediate tap, a capacitiveimpedance device having an intermediate terminal, means connecting saidimpedance device in parallel with said autotransformer across saidcurrent transformer, a potential transformer having a primary windingconnected between said tap and said terminal to have impressed thereon avoltage varying in magnitude and phase in dependence upon the magnitudeand phase of the current in said load circuit, a secondary winding onsaid potential transformer connected to said regulating means forimpressing thereon a control voltage proportional to the voltage of saidprimary winding to cause said regulating means to vary the voltage ofsaid generator in response to variations in the phase and magnitude ofsaid load current, and means for varying the adjustment of said tap toreverse the phase of said control voltage.

3. In combination, an alternating current generator, a load circuitsupplied by said generator, regulating means for controlling the voltageof said generator, and reactive current compensating mean comprising acurrent transformer connected in said load circuit, an autotransformerhaving a pair of end terminals and an intermediate terminal, a reactiveimpedance device having a pair of end terminals and an intermediateterminal, means connecting one of said end terminals or" saidautotransformer to one of said end terminals of said impedance device,means conmeeting the other of said end terminal of said autotransformerto the other of said end terminals of said impedance device to form a.first circuit, means connecting said current transformer across saidfirst circuit, means connected between said intermediate terminals forproducting a control voltage having a magnitude and a phase dependentupon the magnitude and the phase of the current in said load circuit,and means for impressing said control voltage on said regulating meansto cause said regulating means to vary said generator Voltage inresponse to variations in the magnitude and the phase of said loadcurrent, whereby the magnitude of the voltage at a predetermined pointof said load circuit remote from said generator is renderedsubstantially independent of the phase of said load circuit current.

a. In combination, an alternating current generator, a load circuitsupplied by said generator, regulating means for controlling the voltageof said generator, and reactive current compensating means comprising acurrent transformer connected in said load circuit, an autotransformerhaving a pair of end terminals and an intermediate terminal, aninductive impedance device having a pair of end terminals and anintermediate terminal, means connecting one of said end terminals ofsaid autotransformer to one of said end terminals of said impedancedevice, means connecting the other of said end terminals of saidautotransformer to the other of said end terminals of said impedancedevice to form a first circuit, means connecting said currenttransformer across said first circuit, means connected between saidintermediate terminals for producing a control voltage having amagnitude and a phase dependent upon the magnitude and the phase of thecurrent in said load circuit, and means for impressing said controlvoltage on said regulating means to cause said regulating means to varysaid generator voltage in response to variations in the magnitude and inthe phase of said load current, whereby the magnitude of the voltage ata predetermined point of said load circuit remote from said generator isrendered substantially independent of the phase of said load circuitcurrent.

5. In combination, an alternating current genorator, a load circuitconnected to said generator, regulating means for controlling thevoltage of said generator, and reactive current compensating meanscomprising a current transformer connected in said load circuit, anautotransformer having a pair of end terminals and an intermediate tap,a reactive impedance device having a pair of end terminals and aninterme diate terminal, means connecting one of said end terminals ofsaid. impedance device to one of said end terminals of saidautotransformer, means connecting the other of said end terminals ofsaid impedance device to the other of said end terminals of saidautctransformer to form a first circuit, means connecting said currenttransformer across said first circuit, a potential transformer having aprimary winding connected between said intermediate tap and saidintermediate terminal to have impressed thereon a voltage varying inmagnitude and in phase in dependence upon the magnitude and the phase ofthe current in said load circuit, a secondary winding on said potentialtransformer connected to said regulating means for impressing thereon acontrol voltage proportional to the voltage of said primary winding tocause said regulating means to vary said generator voltage in responseto variations in the phase and in the magnitude of said load current,whereby the magnitude of the voltage at a predetermined point of saidload circuit remote from said generator is rendered substantiallyindependent of the phase of said load circuit current, and means forvarying the ad-- justment of said tap to reverse the phase of saidcontrol voltage to change over from overcompounded operation toundercompounded opera- 5 tion.

10 Number Name Date 1,857,174 Zucker May 10, 1932 2,478,623 Crary et alAug. 9, 1949

